The present invention relates to methods of manufacture of printing apparatus, particularly methods of manufacture of droplet deposition apparatus such as inkjet printheads.
Apparatus for deposition of droplets of ink or other fluid are well known. As shown, for example, in EP-A-0 278 590 (belonging to the present applicant and incorporated herein by reference), they comprise one or more ink ejecting chambers from which droplets of ink are ejected, generally via a nozzle, towards a substrate on which an image is to be printed.
To ensure correct positioning of the printed image on the substrate, it is necessary to position the ink ejecting chambers and/or their nozzles accurately relative to the substrate. This is particularly important where several printheads are used to print several overlapping images of different colours (normally cyan, magenta, yellow and black) to provide a full-colour printed image.
Typically, a printer mechanism is employed to hold the substrate relative to a reference surface on the printhead. The printhead is in turn manufactured such that the reference surface lies a fixed distance from the ink ejecting chambers and/or their nozzles of the printing unit (where a printhead has an array of ink ejecting chambers, the reference surface may be positioned relative to a particular one (e.g. the first) of the ink ejecting chambers). However, a tight tolerance on this fixed distance is necessary if the overall positioning of the printhead relative to the substrate is to be to the high accuracy required. Manufacturing the printhead to such tight tolerances may be difficult to achieve, however, and will depend, inter alia, on the material of the printhead, its form and overall dimensions. The present invention seeks to avoid these difficulties.